The present invention relates to a coaxial cable testing and, more particularly, to a coaxial cable testing methods and apparatus that detect intermittent and continuous opens and shorts at junctions between a coaxial cable and terminating coaxial cable connectors. The present invention is generally applicable to all types of connectors for coaxial cables including bayonet coaxial cable (BNC) connectors, threaded connectors and other currently available coaxial cable connectors and connectors which may become available in the future.
Currently almost all customers of cable installation require the testing of every coaxial cable connector terminated in the field. To test coaxial cable connectors in the field, an installer can use a simple battery device with current running through the cables including the connector actuating a buzzer, LCDs, LEDs or a combination thereof to indicate opens or shorts. However, with a simple battery device it is very difficult or impossible to catch intermittent fault conditions because intermittent errors are often too short in duration for the buzzer or LCDs/LEDs to give any indication. Further, field installed cables to be tested often extend over hundreds of feet so that some prior art field testing devices require an installer at each end of the cable, one installer on one end of the cable with the testing device in hand in order to see or hear fault indications and the other installer at the other end of the cable to manipulate the coaxial cable connector on the other end of the cable.
In order to reduce this double testing effort, users can use a Bit Error Rate Test Set (BERT) to detect intermittent or continuous problems at the coaxial cable connector coaxial cable junctions. However, a BERT is very expensive and relatively bulkier than the above describe hand held testers making it difficult to transport in the field.
The prior art discloses a number of coaxial cable testing devices. U.S. Pat. No. 4,553,085 to Canzano discloses a coaxial cable tester device which detects shorts and opens in either the center conductor or the ground conductor of a coaxial cable and indicates the defective conductor. U.S. Pat. No. 5,391,991 to Tuttle discloses a cable shield resistance test set that measures degradation in cable shield without the need to disconnect the cable from the circuit. U.S. Pat. No. 5,477,152 to Hayhurst discloses a cable testing device that tests continuity and/or short circuits automatically in a cable. U.S. Pat. No. 5,565,784 to DeRenne discloses a coaxial cable testing and tracing device that allows the continuity of a plurality of coaxial cables to be tested and to individually locate a coaxial cable.
While these devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not disclose, teach or suggest a coaxial cable connector tester that checks for intermittent and continuous opens and shorts at the junction of the coaxial cable connector and coaxial cable.
In this respect, the coaxial cable connector tester device according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in doing so provides an apparatus primarily developed for the purpose of testing for intermittent and continuous opens and shorts at the junction of the coaxial cable connector and the coaxial cable.
Therefore, it can be appreciated that there exists a continuing need for a new and improved coaxial cable connector testing device which can test for intermittent and continuous opens and shorts at the junction between a coaxial cable connector and a coaxial cable.
This need is met by the coaxial cable connector tester according to the present invention wherein a terminator plug is connected to one connector of a coaxial cable and the connector tester is connected to the other connector. The connector tester applies a voltage to the center conductor of the coaxial cable and a ground to the shield with the voltage at the center conductor being monitored for open and short fault conditions while the cable adjacent first one and then the other connector of the cable are wiggled to test the integrity of the connection of the connectors to the cable. The voltage level on the center conductor changes if either a short or open is present or intermittently occurs during the wiggle operation. To detect shorts and opens, the voltage on the center conductor is monitored by two comparator circuits with one detecting short faults, short comparator, and the other detecting open faults, open comparator. The outputs of the comparator circuits are combined to generate an OK signal if no faults are detected. If open faults are detected, the signals from the open comparator are clocked into a flip-flop and if short faults are detected, the signals from the short comparator are clocked into a flip-flop. Outputs from the flip-flops are counted by respective open and short fault counters and displayed so that the number of intermittent open and short faults, if any, are displayed up to the capacity of the counter and a display used for the tester, 0-8 for the illustrated embodiment. A buzzer can also be used selectively to provide an audible fault signal if desired. A power management circuit provides power to circuitry of the tester as demanded by a user and also monitors a battery so that an indication of low battery power can also be signaled to the user of the tester.
In accordance with one aspect of the present invention, a tester for junctions between a coaxial cable and coaxial cable connectors connected to the coaxial cable to test for intermittent and continuous open circuit and short circuit faults at the junctions comprises a cable terminator plug having a characteristic impedance and being coupled to a first end of a coaxial cable whose junctions are to be tested. An electronic testing circuit having a coaxial cable connector coupled to a second end of the coaxial cable to be tested comprises a test circuit coupled to the coaxial cable connector for detecting open and short circuit faults at one or both of the junctions. The electronic testing circuit generates open fault signals indicating detected open circuit faults, short fault signals indicating detected short faults and a no shorts/no opens signal indicating no detected short or open faults. An open counter coupled to the test circuit counts the open fault signals and a short counter coupled to the test circuit counts the short fault signals. A display circuit displays the counts accumulated in the open counter and the short counter to indicated to a user the number of each type of fault up to the capacity of the counters and the display.
The test circuit may comprise a first comparator coupled to the coaxial cable connector for detecting the open circuit faults and a first storage device responsive to the open circuit faults generates the open fault signals. A second comparator is coupled to the coaxial cable connector for detecting the short circuit faults and a second storage device responsive to the short circuit faults generates the short fault signals. Combination circuitry is coupled to the first and second storage devices for generating the no shorts/no opens signal. The storage devices may comprise flip-flop circuits and the tester may further comprise a battery with the tester being powered by the battery and a power management circuit for controlling power coupled from the battery to the electronic testing circuit. The power management circuit further monitors power of the battery and generates a visual warning displayed by the display circuit if a low power condition exists. Preferably, the power management circuit provides a first low power warning if the power is detected below a first threshold level and a second lower power warning if the power is detected below a second threshold level. For a three volt battery, the first threshold level is approximately 2.6 volts and the second threshold level is approximately 2.45 volts. The power management circuit may comprise an on switch and an off switch and pressing the on switch sets the open counter to a preset value and sets the short counter to a preset level. The preset value for the open counter and the short counter can be equal to zero. The display circuit may be a quad seven segment LCD and may further comprise an audible sounder circuit which generates an audible indication if either the open fault signals or the short fault signals are generated. The audible sounder circuit may comprise a buzzer and may further comprise an on switch and an off switch to turn the buzzer on and off, respectively. In the illustrated embodiment, the electronic testing circuit is accommodated in a tester housing having a window for viewing the display circuit, and including a removable door to insert or remove a power supply battery also accommodated in the tester housing.
In accordance with another aspect of the present invention, a method for testing junctions between a coaxial cable and coaxial cable connectors connected to the coaxial cable for intermittent and continuous open circuit and short circuit faults at the junctions comprises coupling a cable terminator plug having a characteristic impedance to a first end of a coaxial cable whose junctions are to be tested. An electronic testing circuit having a coaxial cable connector is coupled to a second end of the coaxial cable to be tested by coupling a test circuit to the coaxial cable connector to detect open and short circuit faults at one or both of the junctions and to generate open fault signals indicating detected open circuit faults, short fault signals indicating detected short faults and a no shorts/no opens signal indicating no detected short or open faults. A an open counter is coupled to the test circuit for counting the open fault signals, and a short counter is coupled to the test circuit for counting the short fault signals. The counts accumulated in the open counter and the short counter are displayed to the cable installer testing the junctions. The method may further comprise providing a battery to power testing, monitoring power of the battery, and generating a visual warning displayed by a display circuit if a low power condition exists. The step of generating a visual warning may comprise providing a first low power warning if the power is detected below a first threshold level, and providing a second lower power warning if the power is detected below a second threshold level. The method may further comprise providing an audible sounder circuit, and activating the audible sounder circuit to generate an audible indication if either the open fault signals or the short fault signals are generated.
Accordingly, it is an object of the present invention to provide an improved test set that detects intermittent or continuous opens or shorts at the junction of a coaxial cable connector and coaxial cable.
Another object of the present invention is to provided a relatively inexpensive test set that detects intermittent or continuous opens or shorts at the junction of a coaxial cable connector and coaxial cable.
Still another object of the present invention is to provided a test set that detects intermittent or continuous opens or shorts at the junction of a coaxial cable connector and a coaxial cable that is non-bulky and easy to use in the field.
Other objects and advantages of the invention will be apparent from the following detailed description, the accompanying drawings, and the appended claims.